On 14 October 2013, the crew of a Virgin Australia Airlines Boeing 737 aircraft, registered VH VUC, were preparing for a scheduled passenger service from Darwin, Northern Territory to Melbourne, Victoria.
In preparation for the flight, the first officer (FO) prepared two take-off data cards (TODCs), one for a runway 11 full length departure and another for an intersection departure from taxiway ‘Bravo 2’ (B2). The data for a full length departure was entered into the flight management computer (FMC).
The captain conducted an independent check of the take-off performance data and the data entered into the FMC. The TODCs were then placed on the centre pedestal.
The aircraft was taxied to the B2 intersection holding point where the crew were advised by air traffic control of two inbound aircraft, which would delay a full runway length departure. Consequently, the crew elected to depart from the B2 intersection. The FO re programmed the FMC with the take-off performance data previously transcribed on the TODC for that departure and subsequently cross-checked by the captain.
After take off, the crew noted that the TODC for the full runway length departure was visible on the centre pedestal, on top of the intersection departure TODC. The crew discussed whether the take off from the B2 intersection was conducted based on the take-off performance data for a full runway length departure. While the crew were unable to determine what data was used, in the interests of safety, the event was reported.
The operator conducted an investigation into the incident and identified that the aircraft departed from the runway 11 B2 intersection using the take-off performance data for a full length runway departure.
Errors involving take-off performance data calculations and data entry probably occur frequently, but in most cases, there are sufficient defences in place to detect these errors prior to the aircraft leaving the gate. However, as there is varying take-off performance data calculation methods used by airlines, different aircraft involved, and different aircraft systems used to calculate and enter take-off performance data, there is no single solution to ensure that such errors are always prevented or captured.